The outer, protective garments worn by firefighters (commonly referred to as turnout gear) typically include a large coat and pants that have three layers: (1) an outer layer, (2) a intermediate layer providing a vapor barrier, and (3) a removable inner layer providing thermal insulation. The outer layer is fabricated from materials that are resistant to heat, flame, abrasion and water. Firefighters also wear other protective gear, including a helmet, thick gloves, and an air tank that is typically part of a self-contained breathing apparatus (SCBA).
In the 19th century, firefighters in the United States commonly used leather helmets which included a long rear brim and curled up side brims to prevent water from running down the firefighter's neck and into his coat. Around the beginning of the 20th century, firefighters started using aluminum helmets which were molded to look like leather helmets but were less expensive. However, aluminum helmets conducted heat and electricity, causing many firefighters to return to using leather helmets. Leather helmets, which are still popular among firefighters today, are strong enough to provide protection from falling objects, and the large brim of the traditional leather helmets sheds water effectively and prevents objects from dropping down the back of the fire fighter's neck. Leather helmets, however, are very labor intensive and time consuming to manufacture, making them relatively more expensive.
Designers of firefighter helmets must consider a wide array of factors, including, for example, heat, and flame resistance; resistance to electrical current; impact force and acceleration; penetration; chin strap and suspension system effectiveness; flammability and resistance of ear covers; resistance of the face shield to heat and flame; and brightness and surface area of fluorescent markings. In the 1970s, the National Fire Protection Association (NFPA) developed its Standard on Structural Fire Fighter's Helmets. NFPA certification requires that firefighter helmets meet a number of stringent performance requirements.
Modern firefighter helmets are often fabricated from high-tech plastic and composite materials. Such helmets often include a suspension system and energy-absorbing foam impact liners, a face shield and flame-resistant flaps. To satisfy the NFPA standard, firefighter helmets are usually fabricated from highly impact resistant and thermally stable materials such as thermoplastics (for example, a polyetherimide) and thermosets (for example, fiberglass composites including vinylester/polyester thermoset resins). For example, CairnsHELMETS® 1000 and CAIRNS® 1010 helmets, available from Mine Safety Appliances Company (“MSA”), are NFPA approved helmets fabricated from fiberglass composites, which can be reinforced with ballistic-grade KEVLAR® (poly(p-phenyleneterephtalamide, available from Dupont of Wilmington, Del.). Similarly, the CairnsHELMETS® PHOENIX® 660 helmet, available from MSA, is an NFPA approved helmet fabricated from a thermoplastic material.
Thermoplastic helmets, however, have generally been limited to a “modern” or jet-fighter pilot” helmet design in which the helmet brim extends out from the helmet to a much lesser extent and at a greater downward angle relative to horizontal than the brims of a “traditional” helmet design. Prior to the present invention, it was not possible to produce thermoplastic helmets having the extending brim of the traditional helmet design (which typically extends away from the helmet dome by at least 2.5 in. (and, more typically, by at least 3 in.) at, for example, the rear of the helmet) to fully satisfy the NFPA 1971 standard, the disclosure of which is incorporated herein by reference. In that regard, such helmets (and particularly the brims thereof) often do not satisfy the current version of the NFPA 1971 standard for resistance to heat, which limits the deformation a helmet can exhibit under extended exposure to highly elevated temperatures (that is, 5 minutes at a temperature of 500° F.; see, for example, paragraphs 5-2.4, 6-6.2 through 6-6.7 and 6-6.12 of the current version of the NFPA 1971 standard).
However, many firefighters prefer to use helmets having a traditional design. In part, such firefighters prefer the traditional look of such helmets. Moreover, the extending brim of the traditional helmet provides increased protection from falling water and/or objects.
It is desirable, therefore, to develop improved protective helmets (for example, traditional style firefighter helmets) and methods of manufacture thereof.